1. Field of the Invention
The present invention relates generally to the metal tubing working process, and more particularly to a method of and an apparatus for forming a metal tubing stock to any desired tapered shape by means of the swaging process, in and by which a relatively long metal tubing stock can be handled and finished to a tapered shape through a single step of the swaging process.
2. Description of the Prior Art
The metal tubes or hollow rods of relatively great length which are manufactured by means of the swaging process to provide tapered shapes are usually used for the light-equipped poles, flag carrying poles, electrical power wire supports, and other similar purposes. For the manufacture of such articles as mentioned above, the conventional swaging process, which may take place in the form of the method or apparatus, includes multiple steps which are different and separate from each other. An initial stock must be passed through those step-by-step procedures until it can finally be finished to the desired shape. The steps start with cutting a metal blank to a tapered shape in plane, followed by forming it to a tapered tubing with the opposite longitudinal edges left unjoined together. Then, the next step proceeds to cause the edges of the tubing to be joined together by means of the welding process. Any undesired portions that are present along the welded edges of the tubing are removed at the next following step by means of the final polishing or finishing process. The product which has been obtained through the above steps has a relatively simple form or profile, but the manufacture of such a product involves many steps each including a different process as described above. As a whole, a combination of those different and separate processes permits the manufacture of the product, thus making the highly efficient mass production. This increases the manufacturing costs for each item. A single-step swaging process is also known, in which the swaging machine is specifically designed to provide a small-length tapered metal tubing which is analoguous in profile (such as forks for a bicycle which are about 400 mm long). For the long tapered tubes which are totally 4 m to 10 m long, such as the light-equipped poles and others that are mentioned above, it is thought that it is practically impossible to implement the single-step swaging process. Also, there is no swaging machine that provides the single-step swaging processing functions. The present inventor proposed his previous invention that was related to the use of a relatively long spindle in the swaging machine, and was intended to prevent the occurrence of excessive deformation of the spindle, reduction in its rigidity and occurrence of its damage or breakage, which is now published in the official Japanese patent publication No. 57-4421 after the examination. The above invention discloses the spindle which is about 1 m at the longest, which cannot be used for the single-step swaging process that permits the manufacture of 4 m or longer tapered poles. When using that spindle for the manufacture of a 4 m-length tapered pole, at least four steps were required.